title: Oxygen adsorption on the (1×1) and (2×1) reconstructed C(111) surfaces: a density functional theory study.
abstract: The structural and electronic properties, stability, optimum coverage and workfunction of oxygen atoms at different sites on the (1×1) unreconstructed and the (2×1) reconstructed C(111) surfaces have been investigated using density functional theory. Oxygen atoms prefer on-top sites on the C(111)-(1×1) surface, with an optimum coverage of 1/3 monolayers (ML), while on the (2×1) reconstructed surface, bridge sites are preferred with a coverage of 1/2 ML. With increasing oxygen coverage greater than 1/3 ML on the (1×1) surface, a repulsive interaction develops between the oxygen atoms, while for the (2×1) surface such a repulsive interaction occurs for coverages greater than 0.5 ML. For both surfaces, the workfunction initially increases with oxygen adsorption relative to that of each of the clean surfaces, reaching about ∼6 eV and then decreasing slightly at full monolayer coverage. Minimal buckling of the upper π-bonded chains and no dimerization of the clean (2×1) reconstructed surface was observed. An average valence band width of ∼21 eV occurs, and a surface state associated with the (2×1) surface reconstruction was established at ∼-2.5 eV. In addition, O 2s states were established at around -21 eV for the (1×1) surface and at ∼-22.5 eV on the (2×1) surface. These corresponded to similarly located C 2s states at -21.25 eV for both (1×1) and (2×1) surfaces. O 2p states were observed at the Fermi level, ∼-1.25, -2.5, -4.0, and ∼-7.5 eV on the (1×1) surface, and at ∼-2.5 eV, between -4 and -5 eV and at ∼-7.5 eV on the (2×1) surface.
authors.affiliation: Ion Implantation and Surface Studies Program, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa. Trevor.Derry@wits.ac.za
authors.forename: T E
authors.initials: TE
authors.lastname: Derry
authors.forename: N W
authors.initials: NW
authors.lastname: Makau
authors.forename: C
authors.initials: C
authors.lastname: Stampfl
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry*; D003198:Computer Simulation; D018130:Diamond / Q000737:chemistry*; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry*; D011789:Quantum Theory; D013499:Surface Properties
chemical_list: D002244:Carbon; D018130:Diamond; D010100:Oxygen